The organizational state of the double-stranded (ds) RNA in the yeast LA virus capsid is being investigated by cryo-electron microscopy. In most other viruses, ds DNA or RNA is packed with a characteristic inter-duplex spacing of 26 A. In LA virus, this figure is 3540 A suggesting that the fibrillar unit to which it corresponds is larger than a single duplex. STEM measurements of mass/length are being performed on RNA released from disrupted LA capsids compared to purified dsRNA to test this hypothesis. In addition, it was also hoped that one could label empty capsids to aid in the 3-') reconstruction or for use in an in vitro assembly system. There are many cysteines in the major coat protein Gag (and in the Gal-Pol flision protein) but it is not known how many are accessible for Au-labeling. Unfortunately, the capsid preparation was not very pure so Au-labeling was not attempted.